When operating fuel injectors with a coil drive, different opening and closing timing behaviors of individual injectors, and thus variations in the respective injection amounts, occur owing to electrical, magnetic, mechanical and hydraulic tolerances.
The relative injection quantity differences from injector to injector increase as injection times become shorter. Previously, said relative differences in quantity were small and without practical significance. The developments towards smaller injection quantities and shorter injection times, however, result in the influence of the relative differences in quantity no longer being able to be disregarded.